Researchers at the University of Pittsburgh Graduate School of Public Health have identified an enzyme that will trigger the rapid breakdown of several mycobacteria species, including the bacteria known to cause tuberculosis. This discovery could lead to better tests for the deadly disease.
The results of the study, funded by the National Institutes of Health (NIH), are published in the January edition of the Journal of Biological Chemistry.

Tuberculosis is one of the most deadly global bacterial infections, killing more than 2 million people worldwide annually. Doctors see 9 million new cases of the disease every year, mostly in Africa and Southeast Asian countries, although small outbreaks of the disease have been reported in urban areas of the United States. Tuberculosis is caused by bacteria called Mycobacterium tuberculosis. The TB bacteria usually attack the lungs and are spread through the air from one person to another.

"It's a huge public health burden," said Anil Ojha, Ph.D., assistant professor in the Department of Infectious Diseases and Microbiology at Pitt Public Health, and senior author of the study. "Clearly, controlling the infection is heavily dependent upon an effective diagnosis."

The current bacterial culture test for TB infections is highly accurate but time-consuming, taking up to several weeks.

"That may create a race against time for a patient who has acute tuberculosis infection," said Dr. Ojha. "That's why our process is so important. It can obtain results that are both rapid and accurate."

The World Health Organization (WHO) currently recommends a diagnostic technique called nucleic acid-based amplification (NAA); however, this process faces difficulty in breaking open, or lysing bacteria, to access nucleic acids. Mycobacteria are shaped by a thick envelope of fats and sugars, and are resistant to most of the chemicals conventionally used to lyse bacteria.

Pitt Public Health researchers found that exposure to an esterase, an enzyme that targets fatty acids on the surface of the mycobacterial envelope, led to rapid lysis of the bacilli. Researchers also demonstrated that this quick lysis of Mycobacterium tuberculosis improved its detection at lower density.

"Discovery of enzyme-based mycobacteria lysis has the potential to increase the sensitivity of NAA," said Dr. Ojha.

Collaborators on this study include: Yong Yang, Ph.D., Alexandra Bhatti, M.P.H., Danxia Ke, and Peijun Zhang, Ph.D., all of the University of Pittsburgh; Mercedes Gonzalez-Juarrero, Ph.D., and Anne Lenaerts, Ph.D., both of Colorado State University; Laurent Kremer, Ph.D., of the University of Montpellier; and Yann Guerardel, of the French National Center for Scientific Research.

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